High-frequency cavity resonator apparatus



June 22, 1948. A. M. GUREWITSCH HIGH-FREQUENCY CAVITY RESONATOR APPARATUS 4 Sheets-Sheet 1 Filed Jan. 11, 1945 5 w QQ Mm R V mmwrm.

Y X l N 222%??? Inventor Anatoe M. Gurewitsch,

His Attorney.

June 22, 1948.

A. M. GUREWITSC H HIGH-FREQUENCY CAVITY RESONATOR APPARATUS Filed Jan. 11, 1943 4 Sheets-Sheet 2 n n I I I I I I I I I I I I I I I I I I I I I I n I I I I I I I I I I u I Ihvehtorfi Anatde M. GuT-ewitsch, by fi g fjdm is Attorney June 22, 1948. A. M. GUREWITSCH HIGH-FREQUENCY CAVITY RESONATOR APPARATUS Filed Jan. '11, 1943 4 Sheets-Sheet 5 8 9 M M 6 5 7 7 l1 9 3 I W H H 7 W Z l\ pl; 4 P 7 H 6 I M n N 6 W 7 B Q I 8 3 II 6 w 1| w M w w a .H M H.

Inventor;

m w m u t a n His Attorney June 22, 1948. A. M. GUREWIT SC H HIGH-FREQUENCY CAVITY RESONATOR APPARATUS Filed Jan. 11, 1943 4 Sheets-Sheet 4 His Attorney.

fatented June 22 1 9 48 tion of New York HIGH-FREQUENCY CAVITY RESONATOR APPARATUS Anatole M. Gurewitsch, Schenectady, N. Y., assignor to General Electric Company, a corpora- Application January 11, 1943, Serial No. 471,973

10 Claims.

. The present invention relates to high frequency apparatus and is primarily'concerned with the provision of an improved oscillator of the type which employs a discharge device or tube, such as a vacuum triode, as an exciting element.

This application is a continuation-in-part of my copending patent application Serial No. 452,945, filed July 30, 1942, and which is assigned to the assignee of the present application and which noW stands abandoned.

One aspect of satisfactory oscillator design consists in so adjusting the parameters of the system that the level of operation toward which the oscillator tends is one at which satisfactoryoutput and high efficiency are concurrently obtained and at which no excessive loading of any of the oscillator components occurs. A further desired condition is that of stability at the intended operating frequency, and a still further desideratum is the possibility of adjustment for operation over a range of frequencies.

In the ultra high frequency range, especially at frequencies corresponding to wave lengths of the order of a few centimeters, the simultaneous fulfillment of all the indicated conditions becomes extremely difficult because of the relative inflexibility of the circuit elements with which one is obliged to work. Instead of being able to use the easily variable condensers, inductances, etc. which are available at low frequencies, the desired re- 1 sults must be accomplished by such devices as resonant cavity structures, which, for obvious mechanical reasons, are less, readily adjustable as to their electrical properties.

It is an object of my invention to provide new and improved ultra high frequency space resonant systems wherein a new and improved re-entrant type of coupling means is provided with the anode-grid and the grid-cathode circuits of an electric discharge device employed therein.

It is another object of my invention to provide new and improved methods of operating ultra high frequency space resonant systems.

It is a further object of my invention to provide new and improved frequency controllingmeans and coupling means for space-resonant type oscillators wherein not only the magnitude but also the phase of the anode-grid voltage is readily determinable.

It is still another object of my invention to provide a new and improved variable impedance path in a re-entrant type ultra high frequency space resonant oscillator wherein the magnitude or intensity of the electromagnetic radiations delivered to the grid-cathode region are controllable. 1

It is a still further object of my invention to provide new and improved frequency controlling and coupling means for ultra high frequency space resonant systems wherein the tuning operation and control of the coupling means may be efi'ected concurrently or simultaneously.

It is a still further object of the present invention to provide an improved form of high frequency oscillator which is capable of stable operation, high efficiency, and good output and which may be readily adjusted for operation over an appreciable frequency range. In this connection, an important feature of the invention consists in the use of a construction in which the required feedback between the input and output sections of the oscillator is accomplished by the guided propagation of waves established and maintained within a relatively simple form of space resonant cavity. In a particular case, the

desired results are obtained by arranging a vacuum triode within a cavity-forming structure and by providing in connection with the grid of the triode a conductive member which is adapted to form a continuous wave-guiding path between phase and amplitude to assure the efiicient generation of self-sustained oscillations.

The features of the invention desired to be protected herein are pointed out in the appended claims. The invention, itself, together with its further objects and advantages may best be understood by reference to the following description taken in connection with the drawings in which Fig. 1 is a longitudinal sectional view of a high frequency oscillator suitably embodying the invention. Fig. 2 is a sectional view of the triode which is incorporated in the structure of Fig. 1; Fig. 3 is a schematic representation of the structure of Fig. 1; Fig. 4 is a modification of Fig. 1; Figs. 5 and 6 illustrate alternative applications of the invention; Figs. 7 and 8 illustrate further modifications of my invention wherein variable impedance means are provided and associated with the re-entrant type space resonant systems for controlling the electromagnetic radiations emanating from the anode-grid regions; and Fig. 9 is a still further modification wherein there is provided a pair of adjustable tuning members or plungers longitudinally displaced at the ends of the space resonant region for tuning the space resonant system and for controlling the gridcathode voltage.

Referring particularly to Fig. 1, there is shown an oscillator having as its central element a high frequency electric discharge device, such as a triode 10, which is of a type particularly described and claimed in application Serial No. 436,633, filed March 28, 1942, issued as Patent Number 2,416,565 on February 25, 1947, in the name of James E. Beggs and assigned to the General Electric Company, a corporation of New York.

As appears more clearly in Fig. 2 this tube comprises acylindrical anode I l, a grid E 2 and a cylindrical cathode l3, the latter element having its emissive .part in the form of a fiat disk [4 which faces the grid. The envelope within which these electrodes are enclosed comprises a series of three circular metal parts Hi, I! and i8 which are supported in spaced relation by glass cylinders 2B and 2! sealed between them. The part I"! provides a terminal for the grid 12, and a terminal for the anode is provided by a cylindrical enlargement 23 which is welded cor soldered against the upper surface of the part [6.

The cathode i3 is provided at its lower extremity with a flange 25 which parallels the under surfaceof the part is but which is separated from that part by an insulating space-r 2'! (e. g. a mica washer). With this arrangement the .part It has a high frequency connection with the cathode through the capacity existing between this part and the flange 25 but is effectively insulated from the cathode as far as direct current is concerned. Separate direct-curr nt connections are made to the cathode by means of lead-in wires 29 secured to the under surface of the part 25 and tenrninally connected to prongs 3i which depend from the base of the discharge tube. Additional prong-s 3'3 and lead-inwi'res 3d are provided for the purpose of supplying heating current to a coiled filament 35 arranged within the cathode cylinder '43.

The oscillating system in which the tube is incorporated comprises a cavity-forming structure having as a principal component an elongated conductive (e. g. copper or brass) preferably silver plated cylinder 50. This surrounds the tube lfland is symmetrical with respect to the axis of alignment of the electrodes of the tube. A conductive wall part '52 extends across one end of the cylinder 58 and provides a mount for the base of the tube. Near this part there is provided an. annular ring 54 which extends inwardly from the interior wall surface of the cylinder 50 and which is provided at its inner periphery with a ring of spring fingers indicated at These bear upon the exposed surface of the part it and-are thus effectively connected with the cathode is as far as high frequencies are concerned by capacity coupling through the insulating spacer 2? (Fig. 2). A corresponding connection to the anode is made by a solid longitudina'l cylindrical conductor '59 which is supported within the cylinder 50 by [means of a transverse wall part and which is provided at its inner extremity with contact fingers 6i and '82 arranged to engage the anode end of the tube I'll both at the terminal cap 23 and at the periphery of the disk I5. The grid terminal ll is peripherally connected to a tubular conductor 64, whose function will be stated at a later point, and through this connects with a terminal wire 85 which extends through an insulating bead 66 provided in the wall of the cylinder 50.

The D.-C. connections for the triode It may be made in various ways. In the arrangement illustrated, the anode is assumed to be at ground .po- 'tential (i. e. at the potential of the conductive structure as a whole) while the cathode is insulated (in a D.-C. sense) from the main conductive structure by the spacer 21 (Fig. 2) and is made negative with respect to the anode by an appropriate connection to the contact ,prong 31". The grid connection is made through the conductor 65 and if a cathode bias arrangement is to be employed, the connection should be made to the terminal 8S and the resistor 69 adjusted to give the j I-biaswh'ich is required tor most reflective operation.

Like any confined space bounded by a conductive medium, the chamber enclosed by the cylinder 59 provides a system which may be made to resonate electrically at a particular frequency determined by the dimensions and configuration of the chamber and of the elements enclosed by it. This means that under appropriate conditions, electromagnetic waves may be caused to exist within the chamber in a space distribution fixed :by the nature "and location of the exciting source and by the boundary conditions set by the form of the conductive structure. Such waves may be either traveling waves or standing waves (Waves corresponding to a fixed distribution of the'magnetic and electric fields within thechamber) or a combination of traveling and standing waves.

The effective electrical impedance and inductance loss ratio of a space-resonant --structure of the type under consideration are high onoughflso that a structure of *thiskind canbe made to serve as a tank circuit-for an oscillator having an intended operating frequency which is the same as, or is harmonicakll-yrelated to, the resonant frequency of the space :encl'osed by the structure (taking into account theefiect ton resonance of the reaction produced by the exciting tube or other exciting agency). Since resonant frequency is a direct function of the dimensions of the resonator in question, it maybe varied within reasonable limits by appropriate adjustment of these dim'ensions. I-o permit such adjustment in connection with the structure of Fig. "1 there is provided a plunger ii having two sets of contact fingers T2 and 13 which respectively bear upon'the-opposed surface-of the partsbu-andibii. This plun'ger may be .moved back and forth by externally accessible actuating rods "1-5, and by this means the size of the resonant cavity may be adjusted as desired.

Viewing the structure of Fig. 1 a device'ior generating sustained oscillations it may he .noted that the 'triode ill comprises a means for exciting the resonant system provided by the cylinder 50. :If voltagevar iati'ons can he-caused to occur between 'thegrid and anode of the tube all! at the resonant frequency of cylindrical :structure ".50 (as modified by the presence of the tubular condoctor did, the solid cylinder 59 and .the tube itself) electromagnetic waves :of'the frequency sin question will be established in the cavity-forming space. suehwaves'may'be considered-as being initiated fin "the vicinity of the grid-anode gap and as beingpropagated from :thispoint throughout the remainder :of the cavity. Their path of propagation is, governed .in thefirst :instance by the presence :of the :conductive tube 64 which necessarily tends to confine @or :guide the waves along the annular space between this :tube and the outer surface of cylinder .55. At the exr mit f he tub howe e t e es r t e to pass through the l gap indicated at 18, Viewing the mechanism of wave propagation as being a condition of energy flow..it will be seenlthat wave energy issuing from the .gap 78 can flow in the reverse direction along the outside of the 'conductor 6.4. toward the vicinity of the cathode to grid gap of the triode Ill. At this point (as at all other points to which the waves extend) a variable "electric field will be establishe'ddn accordance' with the properties of WZWBS of the type under consideration. Assuming aproper orientation of the electric field axis (actually the only probable orientation withastructure such as that being discussed), potential variations consistent with the variations of the electric field will be set .up between the cathode and grid of the triode. Provided these variations bear a proper phase. relationship'to those previously assumed to.,exist between the grid and anode, it will be seen that a mechanism exists for producing regenerative oscillations.

Thedesired phase relationship under the conditions postulated is thatin which the cathode andanode both have the same sign of potential with respect to the grid atany instant. This is a condition which can evidently exist if the length of the propagating path from the grid-anode gap tothe gricbcathode gap is a full wave length (or anintegral number. of wave lengths) at the operating frequency. Since the dimensions of this path are fixed mainly by those of the tubular conductor 64, it is indicated that the length of this conductor should be approximately a half wave length, so that a wave which traverses the interior of the tube in one direction and its exteriorin the other direction, will have progressed substantially a full wave length. It should be recognized, however, that in calculating the proper length of the tube 64, one must take into account the various end eifects caused by inter electrode impedances and related factors. The importance of these factors can usually best be determined by empirical means and the length of,v the tube 64 adjusted accordingly.

-In addition to a proper phase relationship, which may be obtained in the manner just indicated, it is further necessary that the amplitude of theinput voltage of the triode ll! bear a particular-relationship to its output voltage. In general, and for. reasons which are well known, the. voltage variation at the cathode-grid gap should be less than the anode-cathode varia tion by a factor which is determined mainly by the; amplification factor of the triode. The amplitude relationship obtainable by a construction such as that of Fig. 1 is a function of the degree offeedback and may be adjusted by proper design ofthe elements .of the oscillator structure. The possibility of controlling the relative amplitude of the voltage variation at the grid-anode gap-sand the cathode-grid gap of the triode depends in part upon the consideration that the opening 18 through which feedback occurs represents a discontinuity in the path of propagation of waves originating at the former gap. In accordance with principles well understood in the electronics art, some reflection of wave energy willoccur at this discontinuity and the relative amplitude of the waves developed in the remaining parts of the resonant cavity will be fixed accordingly. By changing the size and configuration of the structural elements involved, almost any desired relationship can be obtained.

Asa result of the considerations stated in the foregoing, it will be seen that the illustrated con struction provides a wave-guiding system which is symmetrical about the central axis of the resonator and which directs high frequency waves initiated between the grid and anode of the tube Ill toward the grid-cathode region of the tube. The length of the wave-guiding path is such that thewwaves'arrive in the right phase to maintain oscillations, and the propagating properties of the path-are such that a desired amplitude relationship is maintained between the input and output voltages of the tube.

In'aisense the system provided may be thought of as one in which the coupling or feedback is complete so that the entire resonator is a single space-resonant cavity having a first region of strong electric field at the anode-grid gap of the enclosed tube and a second such region at the cathode-grid gap of the tube. It may also be considered as an arrangementin which the waveguiding system by Which feedback is produced is itself the resonator which yields the desired impedances across the tube terminals. A system thus constituted is found to be characterized by excellent efficiency in operation and by a high degree of frequency stability.

In order that high frequency energy may be taken from the oscillator for utilization in an external circuit, there is provided a coupling loop 88 which extends into the cavity and which is supported from a hollow tubular conductor 82 extending outwardly through the plunger II. A wire 83 which connects with one extremity of the coupling loop is arranged within the conductor 82 and forms with it a coaxial transmission line.

The operation of the invention will perhaps be more readily understood by reference to Fig. 3 which shows the oscillator of Fig. l in a diagrammatic representation. In this figure elements which may be identified with corresponding parts already described in connection with Fig. 1 are indicated by similar numerals difierentiated by priming.

Fig. 3 particularly illustrates the mechanism by which feedback of the proper character is obtained. Specifically, the dotted line Arepre-' sents the path of propagation of wave energy which originates in the vicinity of the grid-toanode gap B. It will be seen that such wave energy is directed along the annular channel provided between the tubular conductor 64' and the solid cylindrical conductor 59, and then traverses a reversed path along the outside of the conductor 54' toward the cathode-grid gap C. As has been previously stated, it is desired that the effective electrical length of the path be one full wave length at the operating frequency or some integral number of such wave lengths. When this condition is fulfilled, a proper phase relationship for sustained oscillations exists between the voltage variations at B and the voltage variations between the grid and cathode which result from the feedback described.

Referring again to Fig. 1, it will be understood that tuning of the oscillator may be obtained by adjusting the location of the tuning plunger H. Alternatively, some degree of tuning may also be obtained by changing the length of the grid cylinder 64, thus to vary the effective length of the feedback path between the anode-grid gap and the cathode-grid gap. In view of the fact that both the plunger H and the tubular conductor 64 conjointly govern the operating frequency of the oscillator, it is not wholly satisfactory to attempt to tune over any appreciable range by ad justment of either one of these elements alone. It is found, however, that effective concurrent adjustment of them may be obtained by an arrangement such as that illustrated in Fig. 4.

The last named figure illustrates only the ter-- minal portion of an oscillator which as to its remaining parts is assumed to correspond to the construction illustrated in Fig. 1. This comprises a tube of which only the grid and anode terminals are illustrated, these being respectively indi cated at 9| and 92. As in the construction of Fig. I, the anode terminal is connected to a solid cylindrical conductor 93 which extends axially wlth-' in a hollow cavity-forming cylinder 94. A tubu lar conductor 96' having an externally accessible terminal 91 for the application of D.-C. bias serves to control feedback in accordance with principles previously stated herein.

In order to adjust the resonant frequency of the cavity formed within the cylinder 9 there is provided a tuning plunger I which is movable by means of externally accessible actuating. rods till and which bears an output loop I02 which is movable with it. This plunger is connected by an insulating link IM with a cylindrical conductive sleeve I65 which is telescoped over the outer surface of the tubular conductor 96. By virtue of this arrangement, movement of the plunger I06 in either direction produces a concurrent motion of the sleeve I95 and a resultant shortening or lengthening of the feedback path of the oscillator depending upon the direction of the motion involved. It is found that the two tuning controls, 1. e., the plunger Iilil and the sleeve I05, track very well in the arrangement illustrated and that practically level output may be obtained over a tuning range of several centimeters in an oscillator having a median operating Wave length of about ten centimeters.

A further factor which tends to affect the operation of "an oscillator of the type under con-sideration is the location of the grid terminal wire 65 (Fig. 1). Since the magnitude of the effect caused by the Wire is not readily predictable or controllable it is advisable to place the wire at a point which corresponds to a voltage node for the resonator and at which its disturbing inhuence is minimized. In certain cases satisfactory operation has been obtained with the grid and the cylinder 64 floating (i. e. with no ID.-C. connections), but this is not preferable in most instances.

Internal tube capacitance, especially the capacitance' between cathode and anode, also has a bearing on the production of oscillations in that it provides feedback in parallel with that produced by the wave guiding provisions described in the foregoing; This factor is of more or less importance depending on the form of the tube employed and must ordinarily be taken into consideration in the design of apparatus of the'type under consideration.

While the invention has so far been described by reference to a construction in which substantially all of the operative parts are-of cylin=- drical configuration, it shouldbe understood that this is not an essential condition. For example, in an arrangement such as that of Fig. 1, the cylinder 50 and the grid cylinder 64 can alternatively be made of outwardly flared, or frustoconical construction, without seriously modifying the operation on? the oscillator. Many other variations of shape are possible.

A distinctive modification within the scope oi the invention is that illustrated in' Fig. 5. In the latter figure, there isshown partly broken away a three-element discharge tube It'll which may be assumed. to be identical in its internal co'nstruction with the tube-illustrated in Fig. 2 and which includes an anode I-l I a grid I12; and a cathode SE3.

'Ihetube l'iil'is arranged within a rotationally symmetrical cavity formed by the combination of two parallel metallic disks H5 and H6 and an annular metal cylinder IIl which closes the gap between the disks at their peripheries. The anode terminal disk IE0 is in direct contact with the su-rface of the disk -I I5 and a springv finger arrangement indicated at I22 provides a syin= metrical connection between the disk H6 and the envelope part I23 which serves as a high frequency terminal for the cathode II'3. D.-'G.- potential is applied to the cathode and heating current is suppliedto its filament through con tact prongs I25 which depend from the lower extremity of the tube.

In connection with the grid H2, there is provided a radially extending conductive disk or partition I28 which may be formed integrally with the grid terminal, or which may be see ara-tely appended to it. This disk, which-is of smaller diameter than the disks H5, 15,- can nects with a terminal wire I30 by means of which appropriate bias may be applied to the grid.

In the operation of the oscillator, the disk I 28 performs a function analogous to that of the conductive tube 64 of Fig, 1. Tha-t'is to say, it provides a f-ei-idback path of fixed length be tween "the anode-grid gap of the tube I' W and its cathode-grid gap,- the length and proportions of this path beingch'os'en'in such a way as to assure the occurrence of sustained oscillations.

The considerations which govern the props gaz tion of waves in a parallel disk system are set forth in E. D. McArthur Patent No. 2,284,405", granted May 26, 1 42. In general, it maybe said that such waves propagate radially between the opposed disk surfaces in a manner which sug' gests that each elementary radial sector of'the propagating system may be regarded a's a form of parallel wire transmission line. In the ar ra'n'gement illustrated, the course of energy flow as faras the feedback action is concerned isoutwardl'y between the upper surface of the disk I28 and the disk H5 and then inwardly betweenthelower surfaoe'of the'disk I ZB'and the opposed surface oi the disk H6. Obviously,- the radius of the disk I28 determines the length of the-feed back path and thus serves in part to determine the operating frequency of the oscillator. This latter quantity is additionally determined, however, by the overall dimensions of the cavity pro vided by the combined parts I'lli; I16 and H 1.

When the oscillator is in operation, high ire'-' quency energy may be extracted from the em closed space by a coupling loop or probe inserted at an appropriate'point, a loop of suitable char-' acter being indicated at I32.

Fig. 6 represents a modification oi the con-- struction of Fig. 5 in which provisions are made for adjusting the resonant system in such" fash' ion to obtain optimum operatingconditions; The structure illi'i's'trated comprises a vacuiim triode M0 which contains an'anode I4I', agrld I-il and a cathode M3 and which is "arranged centrally within a radial wave systemformedby two parallel metal disks M6 and WI, the outer edges of the disks being connectedby ametallic annulus I 48. Asmall'ei' metal disk IEUWhlOh is connected to thegrid' ofthe triode partially sub divides the resonant cavity and provides a reentrant feedback path between the anode grid gap of the trlode and its'cathode grid gap;

Connection is made'to' the'anode I l-I by means of a cylindrical conductor I 52 which is arranged concentrically within" a second cylindricalcon"-' ductor- I53, a bridging connect-ion beingmadi? between'thetwo cylinders-"by means of a-conduc tive ring I55 which bears appropriately formedcontact fingers' I56. A somewhat similar arrangement used in connection with the cathode comprises an inner conductive cylinder I58"having inwardly directedcontactfingers I59: which bear upon the metal tube part I68 and a second conductive cylinder I62 which surrounds the first cylinder. A conductive plunger I64 which is arranged between the cylinders I58 and IE2 pro vides an adjustable connection between them. The plungers I55 and I64 are connected with externally accessible actuating rods I66 and I61 and may be moved in the axial direction by means of these rods. modify the resonant frequency of the cavity structure as a whole and also changes the effective length of the feedback path between the output and input gaps of the triode I48. By correlated adjustment of both plungers it is possible to adjust both the phase and amplitude of the feedback to assure most effective operation of the oscillator as a whole.

In using the construction of Fig. 6 a D. C. connection is made to the grid through a terminal wire I18 and corresponding connections are made to the cathode through contact prongs I12. As in' the constructions previously described the anode is grounded to the main structure of the resonant cavity. An output loop for the oscillator is indicated at I14.

In accordance with a still further feature of my invention, I provide in ultra high frequency space resonant systems, and particularly space resonant systems wherein re-entrant type feedback means are employed, arrangements for controlling. the degree of coupling between the anode-gri-d and the grid-cathode circuits of the discharge device which may be employed as a central element in such instances. More specifically, I provide in certain of the arrangements described hereinafter means specifically adaptable for controlling the impedance which the electromagnetic waves, derived from the anodegrid regions, encounter in emanating from these regions and consequently in flowing to the gridcathode regions.

7 illustrates one form of my invention wherein such variable impedance means are employed in connection with a re-entrant type ultra high frequency oscillator. In the embodiment illustrated in Fig. '7, a space resonant region is defined principally by a cylindrical conductive member or metallic cylinder I 13 having a flanged part H4 at one end which supports an electric discharge device or tube' I8 illustrated in detail in Fig. 2. The other end of cylinder I13 may be terminated by an apertured disk I15.

A re-entrant type feedback means is employed and may comprise a metallic cylinder I16 electrically connected to disk I1 of tube I and extending an appreciable longitudinal distance within the space resonant region. Cylinder I16 may be supported from the inside of cylinder I13 by a suitable mechanical support which may comprise a dielectric rod I11 sealed to the inside of cylinder I13 and the outer surface of grid cylinder I16.

. Anode part 23 of tube In is connected to a tubular conductor I18 which affords an externally accessible terminal for the application of voltage to the a node II and is provided at the end which engages the anode part 23 with a plurality of longitudinal slots I15 and I88.

As a means for controlling the effective impedance encountered-by the electromagnetic waves generated within the anode-grid region, and. hence for controlling the magnitude or intensity of the electromagnetic waves established within the region between cylinders I13 and I16, I provide a longitudinal cylinder or sleeve I8I, prcf- Motion of the plungers tends to' region IBI' which establishes contact With the longitudinal conductor I 18. Of course, the effective impedance is determined in a substantial measure by the relationship between the inside diameter of cylinder I16 and the outside diameter of sleeve I89. More particularly, it may be stated that the impedance offered by such a concentric arrangement of conductive members is a function of the logarithm of the ratio of the inside diameter of cylinder I16 to the outside diameter of sleeve I8I. Generally speaking, it may be said that the amount of energy which emanates from the anode-grid region depends upon the relative impedances of the anode-grid region and t e impedance at the top of cylinder I16. As the latter impedance approaches the impedance of the anode-grid region, the amount of energy transmitted to the main space resonant region, or the region between cylinders I16 and I13, is increased, due to the fact that as these impedances are made to approach each other the reflection is lessened or reduced.

The magnitude of the impedance offered by sleeve I8I in cooperation with cylinder I16 may be controlled or adjusted by positioning the longitudinal sleeve I 8|. A suitable mechanical expedient may be employed for this purp se and I have chosen to show one form which may oomprise an actuating rod I 84 to which a suitable screw-thread device (not shown) may be connected for accurate positioning of sleeve I8I.

As a means for controlling the natural resonant frequency of the system, I provide an ad- J'ustable end-wall member such as an annular plunger I85 which may be arranged to be in slidable engaement with the inner surface of cylinder I13 and the outer surface of sleeve I8I. Plunger I85 may be actuated by a rod I86, and energy may be derived from the space resonant region by means of suitable output electrode means which may take the form of a loop I81 constituting an extension of an inner conductor I88 comprising part of a concentric transmission line including that conductor and an outer tubular conductor I89.

In the operation of the device shown in Fig. 'I, the sleeve I8I and plunger I85 may be independently or concurrently adjusted to predetermine the operating frequency of the system as a whole, and to control the impedance of the feedback :path. From an elementary point of view, it may be considered that the position of the sleeve I8I controls the magnitude of the oscillations established in the regions between cylinders I13 and I16 and the position of plunger I85 controls the phase and frequency of the electro-v magnetic oscillations established in this region. Of course, there is some interrelation between the two adjustments and the setting of the device for operation at a predetermined frequency may be accomplished by first adjusting one of the members and subsequently adjusting the other to obtain the desired operating frequency and power output. Adjustment of plunger I85 controls the effective electrical length of the space resonant region and consequently determines to some extent the phase of the grid-cathode voltage which lished in the region between cylinders H3 and.

['85 by controlling the efiective impedance to the flow of the oscillations or waves from the anodegrid region. In this arrangement, a longitudinal conductor I99 is connected tothe anode part 23 by means of an adaptor construction [M which is electrically insulated from a longitudinal tubularconductor or sleeve I92 by means of an interspace-d" insulator I93 at one end thereof. The sleeve I92 serves to define with grid cylinder I76 one boundary of the anode-grid region at one end thereof. An annular impedance controlling member I94, preferably of a conductive material, extends into and is in spaced relation with sleeve I92. and cylinder lit. The spacing between the outer surface of annular member 195' and the inner-surface of'cylinder Ht controls principally the magnitude of the electromagnetic oscillations which are generated in the anode-cathode region and which are transmitted to the region defined between cylyinders I73 and I16. Annular member I94 may be mechanically coupled and supported by plunger I95 by means of a plurality of ci'rcumferentially spaced rods I95;

A constant or controllable unidirectional biasing'potential may be impressed on the grid cylinder I16 and hence upon the grid of tube H! by means of a radially extending conductor I96 which constitutes an extension of an inner conductor comprising one part of a coaxial transmission line I91, the outer conductor comprising atubular member I93. Suitable filtering means offers a high impedance to the frequency of the electromagnetic oscillations within the space resonant region and may take the form of a tuned metallic cup-like member E99.

The operation of the embodiment'shown in Fig.

8 is substantially the same as that'described above relative to the embodiment shown in Fig; 7. The

to plunger "35 so that the optimum coupling efiect 5 for a desiredrange of operating frequencies is obtained and thereafter, upon actuation ofrod I86, the tuning and the coupling adjustments are effected concurrently orsimultaneously.

A still further modification of my invention is illustrated in Fig. 9 and is also shown as applied to an ultra high frequency space resonant oscillator of the reentrant type wherein the space region is defined principally by means of'a metallic or conductive cylinder 29!), and wherein the electric discharge device or tube l9 comprises a central control element placed within the space resonant region. A re-entrant type coupling means comprising a conductive or metallic cylinder 29! is placed longitudinally within the space resonant region and extends appreciable-distances in both directions from the plane of the grid member ll. Cylinder 29! may be connected to the grid member H by means of an apertured transverse disk Z92, thelatterofwhich defines oneboundary of the anode-grid. and the grid-cathode regions; Longitudinal anode conductor 203 provides an externally accessible terminal for anode part 23 and is connected thereto by means of an adaptor 299. As a means for minimizing the leakage of high frequency electromagnetic energization present Within the space resonant region, I provide an adjustable longitudinal member 205 which at one end surrounds the-adaptor 2M and may be spaced therefrom. This member maybe moved longitudinally by a suitable screw-thread device 296 having an externally accessible knurled thumb-screw 201. Suitable filtering means comprising. tuned sec-- tions 298 and 209 of concentric-type transmission; linesare interposed in the region between conductor 203 and member 295 to offer a high impedance to the operating frequency of the device and thereby prevent the loss of appreciable en-- ergy within this region.

I provide a pair of adjustable or positionable end-wall members such as annular tuning plungers 219- and 2H at each end of the space resonant regions and which may be respectively actuated by suitable mechanical expedients such as actuating rods 2t! and 2|3. Plunger 21a is adapted to be in slidable engagement with the inner surface of cylinder 2% and the outer surface of a cylindrical supporting member 214' for the: electric discharge device l9; Plunger 2H is also adjustable or in slidable engagement with cylinder 290, and member 205;

As a means for extracting energy from the space resonant system, I provide suitable output electrode means when extends into the anode-grid region and which may assume the form of a loop 2-15 constituting a part' of a con centric transmission line, 216 being externally accessible through an end wall 211. The outer tubular, conductor of concentric transmission line 286 is in slidable engagement with plunger 2H! and extends through an aperture therein. The. position of the loop 2l5 may-be controlled by a suitable screw-thread device 216 which is arranged to. move the concentric transmission line Zilfi longitudinally. Of course, after initial adjustment of the optimum position of the loop 2P5. the plunger. 21! and the concentric transmission line- 26-6 may be mechanically coupled so that upon movement of the plunger 2-H a corresponding adjustment in position-of loop 2l5 is obtained.

A suitable negative unidirectional biasing potential may be impressed on grid cylinder Zlll from an external circuit by means of a concentric: transmission line 218' comprising an inner conductor 219 and an outer tubular conductor 229 within which is placed a filtering means for offering a high impedance to the particular operating frequency or range of frequencies at which thesystem is operated.

In the operation of the device or system shown in Fig. 9 it may be considered that the electromagnetic oscillations are established within the anode-grid region, that is; within the grid cylinder 20! and to the right of' the transverse disk' 2632. Consequently, the position of the loop 2l-5 therein affords a ready means for extracting the high frequency energy and supplying it to a utilization circuit. The electromagnetic waves which supply the grid-,- cathod'evoltage for maintaining the system in oscillation; as explained above, may be considered as progressing first along the inside of cylinder 20! to the right, thence to the left 13 withlnthe region between cylinders 200 and ZOI and, lastly, to the right within the region defined by cylinder 2!".

The natural resonance frequency or the operating frequency of the system is determined by the positions of plungers 2H) and 2H inasmuch as both of these plungers are detrimental in the control of the effective electrical length ofthe space resonant region. Plunger 2! performs an additional function, namely that of controlling the reflected waves during the course of the waves traversing the re-entrant structure. By adjustment of the position of the plunger 2H1, there is offered a ready means for controlling the magnitude and the phase of the gridcathode voltage and consequently a ready means for controlling the power output of the system asv a whole. As will be readily understood by those skilled in the art, the position of plunger 2"! controls the reflection of the electromagnetic waves which are present in the re-entrant portion and consequently permits control of the magnitude and the phase of the grid-cathode voltage.

While the invention has been described by reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without departing from the invention. I, therefore, aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What" I claim as new and desire to secure by Letters Patent of the United States is:

1. High frequency apparatus comprising a cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including acathode, a grid, and an anode defining cathode-grid and anode-grid gaps, a

conductive wall connected to said grid dividing said resonator into a cathode-grid region and an anode-grid region and defining with said resonator a continuous feedback path for'guiding waves from said anode-grid gap to said cathode-grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions of said resonator in energy-exchanging relationship therewith, a conductive member positioned adjacent said conductive wall and a portion of said path, said member being movable to adjust the impedance of said path, and a tuning plunger for varying the dimensions of said resonator adjustably positionable along a dimension thereof, said conductive member being affixed to said plunger whereby said member moves in unison with said plunger. 3 i

2. High frequency apparatus comprising a generally cylindrical cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid, and an anode defining cathode-grid and anode-grid gaps, a generally cylindrical conductive wall connected to said grid dividing said resonator into a'cathode-grid region and an anodegrid region and defining with said resonator a continuous feedback path for guiding waves from said anode-grid gap to said cathode-grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions of said resonator in energy-exchanging relationship therewith, and a generally cylindrical conductive member coaxial with and positioned ad- 14 jacent said conductive wall and a portion of said path, said member determining the impedance of said path and comprising an extension of said wall telescopically mounted with respect thereto and adjustably positionable longitudinally thereof whereby said impedance may be varied;

3. High frequency apparatus comprising a generally cylindrical cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid, and an anode defining cathode-grid and anodegrid gaps, a generally cylindrical conductive wall connected to said grid and extending longitudinally on either side thereof in the direction of said anode and cathode, said wall dividing said resonator into a cathode-grid region and an anode-grid region and defining with said resonator a continuous feedback path forguiding wavesfrom said anode-grid gap to said cathode-grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions of said resonator in energy-exchanging relationship therewith.

4. High frequency apparatus comprising a generally cylindrical cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a, cathode, a'grid, and an anode defining cathode-grid and anodegrid gaps, a generally cylindrical conductive wall connected to said grid dividing said resonator into a cathode-grid region and an anode-grid region and defining with said resonator a continuous feedback path for guiding Waves from said anode-grid gap to said cathode-grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions of said resonator in energy-exchanging, relationship therewith, a tuning plunger for varying the length of said resonator adjustably positionable along the length thereof, a generally cylindrical. conductive member adjustably and coaxially positioned adjacent said conductive wall and a portion of said path for varying the impedance thereof whereby the phase and magnitude of said waves may be controlled, and means rigidly aflixing said member to said plunger whereby said member moves in unison with said plunger.

5. High frequency apparatus comprising a generally cylindrical cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid, and an anode defining cathode-grid and anodes grid gaps, a generally cylindrical conductive wall connected to said grid dividing said resonator into a cathode-grid region and an anode-grid region and defining with saidresonator a continuous feedback path for guiding waves from said anodegrid gap to said cathode-grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions of said resonator in energy-exchanging relationship therewith, a tuning plunger for varying the length of said resonator adjustably positionable along the length thereof, and a generally cylindr-ical conductive member adjustably and coaxially positioned adjacent said conductive wall and a portion of said path for varying the impedance thereof whereby the phase and magnitude of said waves may be controlled, said member comprising an extension-of said plunger telescopically mounted with respect to said Wall.

6. High frequency apparatus comprising inner in: outer concentric conductive cylinders defininga cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid and an anode defining cathode-grid and anode-grid gaps, a cylindrical conductive wall coaxial with said cylinders connected to said grid and dividing said resonator into a cathode-grid region and an anode-grid region and defining with said resonator a continuous feedback-path for guiding Waves from said anode-grid gap to said oathode-grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode having high frequency connections to the outer and inner of said conductive cylinders respectively, a tuning plunger between said cylinders and adjust-ably positionable longitudinally thereof for tuning said resonator, and a cylindrical conductive member coaxially positioned adjacent said conductive wall and a portion of said path, said member being movable to vary the impedance of said path, and means connecting said conductive member to said plunger whereby said member moves in unison with said plunger,

7. High frequency apparatus comprising inner and outer concentric conductive cylinders defining a cavity resonator, an electric discharge device Within said resonator having a plurality of electrodes including a cathode, a grid and anode defining cathode-grid and anode-grid gaps, a cylindrical conductive Wall coaxial with said cylinders connected to said grid and dividing said resonator into a cathode-grid region and an anode-grid region and defining with said resonator a continuous feedback path for guiding Q waves from said anode-grid gap to said cathodegrid gap in proper phase and magnitude to sustain'oscillations in said resonator, said cathode and anode having high frequency connections to the outer and inner of said conductive cylinders respectively, a tuning plunger between said cylinders and adjustably positionable longitudinally thereof for tuning said resonator, and a cylindrical conductive member coaxially positioned adjacent said conductive wall and a portion of said path, said member being slidably mounted upon the inner of said conductive cylinders in telescopic relation to said wall to'vary the impedance of said path.

8. High frequency apparatus comprising inner and outer concentric conductive cylinders defining a cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid and an anode defining cathode-grid and anode-grid gaps, a cylindrical conductive wall coaxial with said cylinders connected to said grid and dividing said resonator into a cathode-grid region and an anode-grid region and defining with said resonator a continuous feedback path for guiding waves from said anode-grip gap to said cathode grid gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode having high frequency connections to the outer and inner of said conductive cylinders respectively, a tuning plunger between said cyl inders and adjustably positionable longitudinally thereof for tuning said resonator, and a cylindrical conductive member coaxially positioned adjacent said conductive wall and a portion of said path, said member being slidably mounted upon the inner of said conductive cylinders in telescopic relation to said wall to vary the im- 16 pedance of said path and' sai'd member havinga restricted portion at the end thereof nearer said anode engaging said inner cylinder.

'9. High frequency apparatus comprising a generally cylindrical cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid, and an anode defining cathode-grid and anode-grld gaps, a conductive wall comprising a cylinder coaxial with said resonator connected to said grid dividing said resonator into a cathode-grid region-and an anode-grid region and defining with said resonator a continuous feedback path for guiding waves from said anodegrid gap to said cathode-grid gap in proper-phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions of said resc-nator in energy-exchanging relationship therewith, and means for controlling the effective electrical length or each of said regions comprising a pair of adjustable end wall members, one at each end of said resonator and constituting portions of the end walls thereof. I

10. High frequency-apparatus comprising a generally cylindrical cavity resonator, an electric discharge device within said resonator having a plurality of electrodes including a cathode, a grid, and an anode defining cathode-grid and anode-grid gaps, a conductive wall comprising a cylinder coaxial with said resonator'connected to said grid dividing said resonator into a cathodegrid region and an anode-grid region'and-defining with said resonator a continuous feedback path for guiding waves from said anode-grid gap to said cathode-grip gap in proper phase and magnitude to sustain oscillations in said resonator, said cathode and anode being connected respectively to different portions: ,.-of said resonator in energy-exchanging relationship-therewith. means for controlling the effective electrical length of each of said regions comprising a pair of adjustable end wall members, one at each end of said resonator and constituting portions of the end walls thereof, and a conductive cylindrical member adjustably and coaxially positioned adjacent said conductive wall for varying the impedance of said path and-thereby the phase and magnitude of said waves.-

ANATOLE M. GUREWITSCH.

REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS;

Date

Number Name 1,979,668 Boddie Nov. 6, 1934 2,088,722 Potter Aug. 3, 1937 2,157,952 Dallenbach May 9, 1939 2,167,201 Dallenbach July 25, 1939 2,242,249 Varian et al. May 20, 1941 2,259,690 Hansen et a1 Oct;21, 1941 2,278,210 Morton Mar. 21, 1942 2,281,717 Samuel May 5, 1942 2,284,405 McAr-thur 'May 26,1942 2,295,680 Mouromtseff et al. Sept. 15,1942 2,304,186 Litton Dec. 8, 1942 2,317,140 Gibson Apr. 20; 1943 2,329,778 Nergaard Sept. 2'1, 1943 2,351,895 Allerding June 20, 1944 2,404,261

Whinnery July 16, 1946 

